docs/README-android.md
author Sam Lantinga <slouken@libsdl.org>
Tue, 11 Dec 2018 20:04:10 -0800
changeset 12473 8a05e33d1b4b
parent 12364 351a67dbe9c6
permissions -rw-r--r--
Fixed building with the 10.10 SDK
     1 Android
     2 ================================================================================
     3 
     4 Matt Styles wrote a tutorial on building SDL for Android with Visual Studio:
     5 http://trederia.blogspot.de/2017/03/building-sdl2-for-android-with-visual.html
     6 
     7 The rest of this README covers the Android gradle style build process.
     8 
     9 If you are using the older ant build process, it is no longer officially
    10 supported, but you can use the "android-project-ant" directory as a template.
    11 
    12 
    13 ================================================================================
    14  Requirements
    15 ================================================================================
    16 
    17 Android SDK (version 26 or later)
    18 https://developer.android.com/sdk/index.html
    19 
    20 Android NDK r15c or later
    21 https://developer.android.com/tools/sdk/ndk/index.html
    22 
    23 Minimum API level supported by SDL: 14 (Android 4.0.1)
    24 
    25 
    26 ================================================================================
    27  How the port works
    28 ================================================================================
    29 
    30 - Android applications are Java-based, optionally with parts written in C
    31 - As SDL apps are C-based, we use a small Java shim that uses JNI to talk to 
    32   the SDL library
    33 - This means that your application C code must be placed inside an Android 
    34   Java project, along with some C support code that communicates with Java
    35 - This eventually produces a standard Android .apk package
    36 
    37 The Android Java code implements an "Activity" and can be found in:
    38 android-project/app/src/main/java/org/libsdl/app/SDLActivity.java
    39 
    40 The Java code loads your game code, the SDL shared library, and
    41 dispatches to native functions implemented in the SDL library:
    42 src/core/android/SDL_android.c
    43 
    44 
    45 ================================================================================
    46  Building an app
    47 ================================================================================
    48 
    49 For simple projects you can use the script located at build-scripts/androidbuild.sh
    50 
    51 There's two ways of using it:
    52 
    53     androidbuild.sh com.yourcompany.yourapp < sources.list
    54     androidbuild.sh com.yourcompany.yourapp source1.c source2.c ...sourceN.c
    55 
    56 sources.list should be a text file with a source file name in each line
    57 Filenames should be specified relative to the current directory, for example if
    58 you are in the build-scripts directory and want to create the testgles.c test, you'll
    59 run:
    60 
    61     ./androidbuild.sh org.libsdl.testgles ../test/testgles.c
    62 
    63 One limitation of this script is that all sources provided will be aggregated into
    64 a single directory, thus all your source files should have a unique name.
    65 
    66 Once the project is complete the script will tell you where the debug APK is located.
    67 If you want to create a signed release APK, you can use the project created by this
    68 utility to generate it.
    69 
    70 Finally, a word of caution: re running androidbuild.sh wipes any changes you may have
    71 done in the build directory for the app!
    72 
    73 
    74 For more complex projects, follow these instructions:
    75     
    76 1. Copy the android-project directory wherever you want to keep your projects
    77    and rename it to the name of your project.
    78 2. Move or symlink this SDL directory into the "<project>/app/jni" directory
    79 3. Edit "<project>/app/jni/src/Android.mk" to include your source files
    80 
    81 4a. If you want to use Android Studio, simply open your <project> directory and start building.
    82 
    83 4b. If you want to build manually, run './gradlew installDebug' in the project directory. This compiles the .java, creates an .apk with the native code embedded, and installs it on any connected Android device
    84 
    85 Here's an explanation of the files in the Android project, so you can customize them:
    86 
    87     android-project/app
    88         build.gradle            - build info including the application version and SDK
    89         src/main/AndroidManifest.xml	- package manifest. Among others, it contains the class name of the main Activity and the package name of the application.
    90         jni/			- directory holding native code
    91         jni/Application.mk	- Application JNI settings, including target platform and STL library
    92         jni/Android.mk		- Android makefile that can call recursively the Android.mk files in all subdirectories
    93         jni/SDL/		- (symlink to) directory holding the SDL library files
    94         jni/SDL/Android.mk	- Android makefile for creating the SDL shared library
    95         jni/src/		- directory holding your C/C++ source
    96         jni/src/Android.mk	- Android makefile that you should customize to include your source code and any library references
    97         src/main/assets/	- directory holding asset files for your application
    98         src/main/res/		- directory holding resources for your application
    99         src/main/res/mipmap-*	- directories holding icons for different phone hardware
   100         src/main/res/values/strings.xml	- strings used in your application, including the application name
   101         src/main/java/org/libsdl/app/SDLActivity.java - the Java class handling the initialization and binding to SDL. Be very careful changing this, as the SDL library relies on this implementation. You should instead subclass this for your application.
   102 
   103 
   104 ================================================================================
   105  Customizing your application name
   106 ================================================================================
   107 
   108 To customize your application name, edit AndroidManifest.xml and replace
   109 "org.libsdl.app" with an identifier for your product package.
   110 
   111 Then create a Java class extending SDLActivity and place it in a directory
   112 under src matching your package, e.g.
   113 
   114     src/com/gamemaker/game/MyGame.java
   115 
   116 Here's an example of a minimal class file:
   117 
   118     --- MyGame.java --------------------------
   119     package com.gamemaker.game;
   120     
   121     import org.libsdl.app.SDLActivity; 
   122     
   123     /**
   124      * A sample wrapper class that just calls SDLActivity 
   125      */ 
   126     
   127     public class MyGame extends SDLActivity { }
   128     
   129     ------------------------------------------
   130 
   131 Then replace "SDLActivity" in AndroidManifest.xml with the name of your
   132 class, .e.g. "MyGame"
   133 
   134 
   135 ================================================================================
   136  Customizing your application icon
   137 ================================================================================
   138 
   139 Conceptually changing your icon is just replacing the "ic_launcher.png" files in
   140 the drawable directories under the res directory. There are several directories
   141 for different screen sizes.
   142 
   143 
   144 ================================================================================
   145  Loading assets
   146 ================================================================================
   147 
   148 Any files you put in the "app/src/main/assets" directory of your project
   149 directory will get bundled into the application package and you can load
   150 them using the standard functions in SDL_rwops.h.
   151 
   152 There are also a few Android specific functions that allow you to get other
   153 useful paths for saving and loading data:
   154 * SDL_AndroidGetInternalStoragePath()
   155 * SDL_AndroidGetExternalStorageState()
   156 * SDL_AndroidGetExternalStoragePath()
   157 
   158 See SDL_system.h for more details on these functions.
   159 
   160 The asset packaging system will, by default, compress certain file extensions.
   161 SDL includes two asset file access mechanisms, the preferred one is the so
   162 called "File Descriptor" method, which is faster and doesn't involve the Dalvik
   163 GC, but given this method does not work on compressed assets, there is also the
   164 "Input Stream" method, which is automatically used as a fall back by SDL. You
   165 may want to keep this fact in mind when building your APK, specially when large
   166 files are involved.
   167 For more information on which extensions get compressed by default and how to
   168 disable this behaviour, see for example:
   169     
   170 http://ponystyle.com/blog/2010/03/26/dealing-with-asset-compression-in-android-apps/
   171 
   172 
   173 ================================================================================
   174  Pause / Resume behaviour
   175 ================================================================================
   176 
   177 If SDL is compiled with SDL_ANDROID_BLOCK_ON_PAUSE defined (the default),
   178 the event loop will block itself when the app is paused (ie, when the user
   179 returns to the main Android dashboard). Blocking is better in terms of battery
   180 use, and it allows your app to spring back to life instantaneously after resume
   181 (versus polling for a resume message).
   182 
   183 Upon resume, SDL will attempt to restore the GL context automatically.
   184 In modern devices (Android 3.0 and up) this will most likely succeed and your
   185 app can continue to operate as it was.
   186 
   187 However, there's a chance (on older hardware, or on systems under heavy load),
   188 where the GL context can not be restored. In that case you have to listen for
   189 a specific message, (which is not yet implemented!) and restore your textures
   190 manually or quit the app (which is actually the kind of behaviour you'll see
   191 under iOS, if the OS can not restore your GL context it will just kill your app)
   192 
   193 
   194 ================================================================================
   195  Threads and the Java VM
   196 ================================================================================
   197 
   198 For a quick tour on how Linux native threads interoperate with the Java VM, take
   199 a look here: https://developer.android.com/guide/practices/jni.html
   200 
   201 If you want to use threads in your SDL app, it's strongly recommended that you
   202 do so by creating them using SDL functions. This way, the required attach/detach
   203 handling is managed by SDL automagically. If you have threads created by other
   204 means and they make calls to SDL functions, make sure that you call
   205 Android_JNI_SetupThread() before doing anything else otherwise SDL will attach
   206 your thread automatically anyway (when you make an SDL call), but it'll never
   207 detach it.
   208 
   209 
   210 ================================================================================
   211  Using STL
   212 ================================================================================
   213 
   214 You can use STL in your project by creating an Application.mk file in the jni
   215 folder and adding the following line:
   216 
   217     APP_STL := c++_shared
   218 
   219 For more information go here:
   220 	https://developer.android.com/ndk/guides/cpp-support
   221 
   222 
   223 ================================================================================
   224  Using the emulator
   225 ================================================================================
   226 
   227 There are some good tips and tricks for getting the most out of the
   228 emulator here: https://developer.android.com/tools/devices/emulator.html
   229 
   230 Especially useful is the info on setting up OpenGL ES 2.0 emulation.
   231 
   232 Notice that this software emulator is incredibly slow and needs a lot of disk space.
   233 Using a real device works better.
   234 
   235 
   236 ================================================================================
   237  Troubleshooting
   238 ================================================================================
   239 
   240 You can see if adb can see any devices with the following command:
   241 
   242     adb devices
   243 
   244 You can see the output of log messages on the default device with:
   245 
   246     adb logcat
   247 
   248 You can push files to the device with:
   249 
   250     adb push local_file remote_path_and_file
   251 
   252 You can push files to the SD Card at /sdcard, for example:
   253 
   254     adb push moose.dat /sdcard/moose.dat
   255 
   256 You can see the files on the SD card with a shell command:
   257 
   258     adb shell ls /sdcard/
   259 
   260 You can start a command shell on the default device with:
   261 
   262     adb shell
   263 
   264 You can remove the library files of your project (and not the SDL lib files) with:
   265 
   266     ndk-build clean
   267 
   268 You can do a build with the following command:
   269 
   270     ndk-build
   271 
   272 You can see the complete command line that ndk-build is using by passing V=1 on the command line:
   273 
   274     ndk-build V=1
   275 
   276 If your application crashes in native code, you can use ndk-stack to get a symbolic stack trace:
   277 	https://developer.android.com/ndk/guides/ndk-stack
   278 
   279 If you want to go through the process manually, you can use addr2line to convert the
   280 addresses in the stack trace to lines in your code.
   281 
   282 For example, if your crash looks like this:
   283 
   284     I/DEBUG   (   31): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 400085d0
   285     I/DEBUG   (   31):  r0 00000000  r1 00001000  r2 00000003  r3 400085d4
   286     I/DEBUG   (   31):  r4 400085d0  r5 40008000  r6 afd41504  r7 436c6a7c
   287     I/DEBUG   (   31):  r8 436c6b30  r9 435c6fb0  10 435c6f9c  fp 4168d82c
   288     I/DEBUG   (   31):  ip 8346aff0  sp 436c6a60  lr afd1c8ff  pc afd1c902  cpsr 60000030
   289     I/DEBUG   (   31):          #00  pc 0001c902  /system/lib/libc.so
   290     I/DEBUG   (   31):          #01  pc 0001ccf6  /system/lib/libc.so
   291     I/DEBUG   (   31):          #02  pc 000014bc  /data/data/org.libsdl.app/lib/libmain.so
   292     I/DEBUG   (   31):          #03  pc 00001506  /data/data/org.libsdl.app/lib/libmain.so
   293 
   294 You can see that there's a crash in the C library being called from the main code.
   295 I run addr2line with the debug version of my code:
   296 
   297     arm-eabi-addr2line -C -f -e obj/local/armeabi/libmain.so
   298 
   299 and then paste in the number after "pc" in the call stack, from the line that I care about:
   300 000014bc
   301 
   302 I get output from addr2line showing that it's in the quit function, in testspriteminimal.c, on line 23.
   303 
   304 You can add logging to your code to help show what's happening:
   305 
   306     #include <android/log.h>
   307     
   308     __android_log_print(ANDROID_LOG_INFO, "foo", "Something happened! x = %d", x);
   309 
   310 If you need to build without optimization turned on, you can create a file called
   311 "Application.mk" in the jni directory, with the following line in it:
   312 
   313     APP_OPTIM := debug
   314 
   315 
   316 ================================================================================
   317  Memory debugging
   318 ================================================================================
   319 
   320 The best (and slowest) way to debug memory issues on Android is valgrind.
   321 Valgrind has support for Android out of the box, just grab code using:
   322 
   323     svn co svn://svn.valgrind.org/valgrind/trunk valgrind
   324 
   325 ... and follow the instructions in the file README.android to build it.
   326 
   327 One thing I needed to do on Mac OS X was change the path to the toolchain,
   328 and add ranlib to the environment variables:
   329 export RANLIB=$NDKROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/darwin-x86/bin/arm-linux-androideabi-ranlib
   330 
   331 Once valgrind is built, you can create a wrapper script to launch your
   332 application with it, changing org.libsdl.app to your package identifier:
   333 
   334     --- start_valgrind_app -------------------
   335     #!/system/bin/sh
   336     export TMPDIR=/data/data/org.libsdl.app
   337     exec /data/local/Inst/bin/valgrind --log-file=/sdcard/valgrind.log --error-limit=no $*
   338     ------------------------------------------
   339 
   340 Then push it to the device:
   341 
   342     adb push start_valgrind_app /data/local
   343 
   344 and make it executable:
   345 
   346     adb shell chmod 755 /data/local/start_valgrind_app
   347 
   348 and tell Android to use the script to launch your application:
   349 
   350     adb shell setprop wrap.org.libsdl.app "logwrapper /data/local/start_valgrind_app"
   351 
   352 If the setprop command says "could not set property", it's likely that
   353 your package name is too long and you should make it shorter by changing
   354 AndroidManifest.xml and the path to your class file in android-project/src
   355 
   356 You can then launch your application normally and waaaaaaaiiittt for it.
   357 You can monitor the startup process with the logcat command above, and
   358 when it's done (or even while it's running) you can grab the valgrind
   359 output file:
   360 
   361     adb pull /sdcard/valgrind.log
   362 
   363 When you're done instrumenting with valgrind, you can disable the wrapper:
   364 
   365     adb shell setprop wrap.org.libsdl.app ""
   366 
   367 
   368 ================================================================================
   369  Graphics debugging
   370 ================================================================================
   371 
   372 If you are developing on a compatible Tegra-based tablet, NVidia provides
   373 Tegra Graphics Debugger at their website. Because SDL2 dynamically loads EGL
   374 and GLES libraries, you must follow their instructions for installing the
   375 interposer library on a rooted device. The non-rooted instructions are not
   376 compatible with applications that use SDL2 for video.
   377 
   378 The Tegra Graphics Debugger is available from NVidia here:
   379 https://developer.nvidia.com/tegra-graphics-debugger
   380 
   381 
   382 ================================================================================
   383  Why is API level 14 the minimum required?
   384 ================================================================================
   385 
   386 The latest NDK toolchain doesn't support targeting earlier than API level 14.
   387 As of this writing, according to https://developer.android.com/about/dashboards/index.html
   388 about 99% of the Android devices accessing Google Play support API level 14 or
   389 higher (October 2017).
   390 
   391 
   392 ================================================================================
   393  A note regarding the use of the "dirty rectangles" rendering technique
   394 ================================================================================
   395 
   396 If your app uses a variation of the "dirty rectangles" rendering technique,
   397 where you only update a portion of the screen on each frame, you may notice a
   398 variety of visual glitches on Android, that are not present on other platforms.
   399 This is caused by SDL's use of EGL as the support system to handle OpenGL ES/ES2
   400 contexts, in particular the use of the eglSwapBuffers function. As stated in the
   401 documentation for the function "The contents of ancillary buffers are always 
   402 undefined after calling eglSwapBuffers".
   403 Setting the EGL_SWAP_BEHAVIOR attribute of the surface to EGL_BUFFER_PRESERVED
   404 is not possible for SDL as it requires EGL 1.4, available only on the API level
   405 17+, so the only workaround available on this platform is to redraw the entire
   406 screen each frame.
   407 
   408 Reference: http://www.khronos.org/registry/egl/specs/EGLTechNote0001.html
   409 
   410 
   411 ================================================================================
   412  Known issues
   413 ================================================================================
   414 
   415 - The number of buttons reported for each joystick is hardcoded to be 36, which
   416 is the current maximum number of buttons Android can report.
   417